Vangaurd used an unorthodox structure to pass wealth on to their customers. Their unusual structure apparently creates a contradiction with the letter of current tax law even if they are clearly within the spirit. Everyone quoted is on the "whistle blowers" legal team and there are no comments from the IRS. Danon is more patent troll than whistleblower. He'll get paid off and vanguard will get an exception that validates their operating structure.
No way the IRS will just demand $35B (the number I saw quoted in another even more speculative article in this suit) - that would destroy the company and the US govt is not in the business of destroying large businesses.... Especially for the sin of passing wealth into the pockets of average Americans. Sadly, this "story" is making the rounds on the internet dailies because they'll print anything with a big number and a "corporations are evil" subtext.
Clickbait....Clickbait never changes.